1. Field of the Invention
The present invention relates to an accelerating system for improving the running speed of a bicycle, which is capable of enhancing a rotational force of a drive wheel and is compatible with a conventional chain gear if so desired, by simply installing the accelerating system in a hub shaft of the chain-driven bicycle.
2. Description of the Prior Art
In general, bicycles have been used for a long time as traffic means along with the history of human development. Until recently, bicycles are used widely throughout the world for the purpose of sport, entertainment, tourism or outdoor recreation activity.
Typically, a bicycle comprises a body frame having a front wheel at a front part an a rear wheel (hereinafter, so called “drive wheel”) at a rear part thereof, a pair of pedals fixed at both sides of a shaft of which a crank is axially fixed thereon, and a power transmission means to transfer the power generated by rotation of the pedals to the drive wheel via a chain. The power transmission means includes a driving sprocket mounted at the pedals, a driven sprocket having a latch for transmitting power toward the drive wheel, and the chain to connect the driving sprocket to the driven sprocket.
Recently, a variety of endeavors for improving the running speed of the bicycle have been proposed. For example, transmission systems for easily changing the position of the linking chain by installing the multi-step transmission sprocket assembly at a one side of the drive chain gear of the pedals and the drive wheel have been proposed.
FIG. 1 is a schematic view for showing the power transmission between the front chain wheel and the rear drive wheel in a general bicycle. As shown in FIG. 1, the conventional bicycle travels in the forward direction by a rotation power that is generated by rotating the pedals forward and transmitted through the chain (c) extending between the front chain gear (S1) mounted at the shaft of pedals and the rear chain gear (S2) mounted at the drive wheel 10.
Meanwhile, a small bicycle such as a folding bicycle has been developed for the purpose of simple transportation and safekeeping. The folding bicycle incorporates special design features such as small wheels and light body frame enabling the bike to fold into a compact form, thereby facilitating transport or storage.
However, one drawback of such conventional small bicycle is that the operation for increasing the running speed thereof is troublesome. Since this small bicycle is provided with small wheels, the user must to press down the pedals with all his or her force so as to quickly rotate the drive wheels. Accordingly, it is impossible to continuously increase the running speed of the bicycle. This results in the limitation use for the folding bicycle.
Although the user can drive the general bicycle having relatively large wheels at a higher speed faster than the running speed of the small bicycle having relatively small wheels, it is necessary to have much more power than the small bicycle requires the user do.
In order to solve these disadvantages, a variety of driving systems for a bicycle have been proposed. One approach is, a driving gear of bike including a planetary gear system has been proposed on Korean Registered Utility Model No. 20-418803 issued to Si-Cheol KIM on Jun. 8, 2006.
This utility model has suggested an improved internal structure for a bicycle such as tricycles for an infant or young children, unicycle, ordinary-type cycle, which did not have any planetary gear system for transmitting the driving power between the pedals and drive wheels. That is, this utility model employed the planetary gear system including a ring gear, a planetary gear and a sun gear so as to increase the running speed of the bicycle.
As well known in the related technical art, the planetary gear is engaged with the sun gear and it revolves around the sun gear. When the planetary gear is engaged with the ring gear and simultaneously rotates along the inner circumferential surface of the ring gear, it rotates on its axis. The planetary gear system is a sort of the transmission for the purpose of rapidly rotating a rotational body by allowing the sun gear to be rotated at a high speed.
In the above Korean Registered Utility Model employing the planetary gear system as described above, the planetary gear is mounted to the pedals so that the user directly presses down the pedals so as to rotate the drive wheels. Then, individual gears may rotate in proportion to the number of rotations of the pedals, thereby resulting in increase of the number of rotation of the wheels due to cooperative operation of the gears.
Since the planetary gear system is installed on the rotational shaft of which the pedals are fixed at both sides thereof in the bicycle such as tricycles for an infant or young children, unicycle, ordinary-type cycle as described above, the application thereof is practically limited depending on the design of bicycle. Another drawback of the conventional planetary gear system is that the running speed of the bicycle can not be substantially enhanced because the main power is generated by the pedals.
It is also known to provide another type of bicycle comprising the planetary gear system installed at the front chain gear (S1). In other words, the sun gear is mounted onto the rotational shaft of which a pair of pedals is fixed at both sides thereof, and three planetary gears are installed within a housing of which a ring gear is provided by using a fixed disk. When the pedals are stepped by the user for forward traveling, the shaft begins to rotate, which in turn rotates the chain gear (S1) and the sun gear. The planetary gears are engaged with the ring gear and they gradually travel along the ring gear, and thereby resulting in the transmitting of driving power via the chain to the drive wheel.
However, this type of bicycle is developed for the purpose of weight training or easily climbing an upward sloping road, but not improving the running speed of the bicycle. In other words, in order to enhance the physical health, the user can take up this type of bicycle employing the gear reduction structure which involves using gears/sprockets/pulleys of different sizes to work together. Also, if the user presses down the pedal of this bicycle with relatively small power, it is possible to easily climb an upward sloping road with riding this bicycle. However, this bicycle has still disadvantage that it has the planetary gear system which cannot be adapted to enhance the running speed of the bicycle.
In the meantime, another approach is, an accelerating system for improving the running speed of a bicycle has been proposed on Korean Patent Registered No. 10-0901436 issued to the present applicant on Jun. 1, 2009 with the title of “Accelerator for bicycle for driving speed elevation”. However, one drawback of this conventional accelerator for bicycle is that the width dimension thereof in one lateral direction on the hub shaft is too large and thereby resulting in damage to the accelerator due to interference or collision with other objects during operation of the bicycle. Another drawback of the conventional accelerator for bicycle is that it may not be compatible with a conventional chain gear.